238 HISTORY OF BRITISH FERNS. 



pauperated forms, depending, no doubt, on the circumstances 

 of their growth. They differ from the ordinary plant in 

 being altogether smaller, the height ranging from two to 

 four or five inches, the lower part of the stems being de- 

 cumbent, and the whole stem almost devoid of branches ; 

 a few being developed only at their very base. In some 

 states, this form has much resemblance to the prostrate 

 E. variegatum, but is distinguishable by means of its 

 sheaths and fructification. 



The variety, or form, called polystachion, is probably 

 rather accidental than constant, and is to be regarded as 

 the result of peculiar and changeable circumstances which 

 may influence its growth. The variety nudum, or aljsinum, 

 seems clearly a depauperization of the plant, either through 

 elevation or lack of food, both producing the result of a 

 dwarf stunted growth. "We have had no opportunity of 

 testing their constancy in cultivation, neither are we aware 

 of any experiments having been made on this point, but 

 we should expect they would both revert to the common 

 form under the influences of domestication. 



EQUISETUM SYLVATICUM, Linn&us. The Wood Horsetail. 

 (Plate XX. fig. 3.) 



Perhaps this may be called the most beautiful of the 



